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  #1  
Old 09-07-2021, 08:10 AM
Jesse's Avatar
Jesse Jesse is offline
 
Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,711
Default Radio range issues

We are having a problem that I wanted to post here to see if anybody here has a valuable suggestion. In a new RV-10 with a professional audio harness (Approach Fast Stack), we are having problem with receive range on our radios. We have a GMA245 audio panel, a Dynon Com (Trig Transceiver) and a GTN650. This has been an ongoing problem that didn't appear at first, but became noticeable around 10-15 hours from new.

On a test the other day, the plane left here. From our base station radio with an antenna on the top of the hangar, we had great reception for the first couple of miles. The further he got away, the more weak and staticy the plane received, although the transmit was still loud and clear. When the plane was 15 miles away, he could not receive the base station at all, and he was still loud and clear receiving at the base station. In summary, his receive range is very short, but transmit seems to be good, or at least better. This problem is with both radios.

We have verified that we have good coax from both radios. to their respective antennas, which are the RAMI AV-17's, and the coax run down opposite sides of the plane to their respective antennas. Both antennas were new when installed and bought together. We removed some paint where the screws attach the antenna to the airplane, and used lock washers under the nuts after removing primer from where the nuts tighten down, so we know we have a good ground (the antennas are under the pilot and copilot seats). We have tested with each radio powered down and the problem is still with the powered radio, so it isn't cross-talk. We have verified, and added, a good ground from the audio panel to the airframe. We have tried with both pilot and copilot headset alone, with an without the rear headsets, and have tried other known good headsets. We have replaced the Dynon transceiver 2 or 3 times, thinking it was specific to that radio, with no change. The intercom works just fine all the way around. We have swapped with another GMA245 audio panel and there was no change, so it's not a bad audio panel.

The only thing we can think of that is left to check is to replace one or both of the COM antennas. I have never had a bad RAMI bent whip antenna, certainly not out of the box, and the likelihood of two at the same time on the same plane seems even more unlikely, unless they were both from the same batch that happened to be a bad batch, but I don't know how we would change that.

As a side note, this plane has the full EFII system with the buss manager. We are going to test reception range on the ground with the engine on and off soon to see if the engine could be causing any disruption.

Any thoughts?
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  #2  
Old 09-07-2021, 08:32 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,174
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Considering you state that both radios have the same problem, I suggest both antennas and/or feed lines failing at the same time in the same way is not a high probability. Here however a few minutes with a real antenna analyzer to ring out the system would quickly confirm this assumption.

If the antenna, feed lines and fittings are good, then look at the radios - or more specifically a common fault that will degrade receiver sensitivity on both radios.

So:
- Did you eliminate RF noise makers (USB chargers, led Nav/Strobes, led landing lights and such) to verify the problem still present?
- Did you change anything, like connecting the Garmin “receiver de-sensation” line on the GTN-650?
- Did you try bypassing the audio panel (turning it off) so you have a direct connection between the headset and radio?

Side note - scraping paint on an antenna mount is not required or desired. Using star washers on the inside is more than adequate.

Carl

Last edited by Carl Froehlich : 09-07-2021 at 08:44 AM.
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  #3  
Old 09-07-2021, 08:40 AM
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dpansier dpansier is offline
 
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Location: Green Bay, WI (GRB)
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Have you completed your testing with another base station or aircraft? Could be a problem with your base station.
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  #4  
Old 09-07-2021, 08:55 AM
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Jesse Jesse is offline
 
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Location: X35 - Ocala, FL
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Quote:
Originally Posted by dpansier View Post
Have you completed your testing with another base station or aircraft? Could be a problem with your base station.
We did the specific testing with the base station because he was seeing the problem in flight. It is not a base station problem.
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  #5  
Old 09-07-2021, 09:00 AM
Jesse's Avatar
Jesse Jesse is offline
 
Join Date: May 2005
Location: X35 - Ocala, FL
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Quote:
Originally Posted by Carl Froehlich View Post
Considering you state that both radios have the same problem, I suggest both antennas and/or feed lines failing at the same time in the same way is not a high probability. Here however a few minutes with a real antenna analyzer to ring out the system would quickly confirm this assumption.

If the antenna, feed lines and fittings are good, then look at the radios - or more specifically a common fault that will degrade receiver sensitivity on both radios.

So:
- Did you eliminate RF noise makers (USB chargers, led Nav/Strobes, led landing lights and such) to verify the problem still present?
- Did you change anything, like connecting the Garmin “receiver de-sensation” line on the GTN-650?
- Did you try bypassing the audio panel (turning it off) so you have a direct connection between the headset and radio?

Side note - scraping paint on an antenna mount is not required or desired. Using star washers on the inside is more than adequate.

Carl
We have turned on and off just about all things that could be turned off, although possibly not the USB chargers, which we have never had a problem with. We will try that.
We did not change anything, but there could be a setting to change that. I have a hard time seeing how we could have the same problem with both radios if it were something like that.
We have not tried turning off the audio panel. We tried a different audio panel, but that is a good thought.

Thanks.
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  #6  
Old 09-07-2021, 09:28 AM
jclark jclark is offline
 
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Location: Columbia, SC
Posts: 837
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Quote:
Originally Posted by Jesse View Post
We have turned on and off just about all things that could be turned off, although possibly not the USB chargers, which we have never had a problem with. We will try that.
We did not change anything, but there could be a setting to change that. I have a hard time seeing how we could have the same problem with both radios if it were something like that.
We have not tried turning off the audio panel. We tried a different audio panel, but that is a good thought.

Thanks.
+1 on receiver sensitivity being affected as a possibility.

Another easy thing to try is:
(Forgive me if you have already done all of this. Just throwing out ideas),

1. Push the plane into the metal hangar and close the doors.
2. Tune in ATIS. If it is very strong try a station that is weaker. One that you can barely receive.
3. Turn everything on and one by one, everything off, and see if you detect any difference. Being on the ground without engine noise may help locate the problem.

An alternative is to have the plane outside and dial in the weakest ATIS you can find. Repeat above but with the engine (EI) running and not running.

Totally different matter ... is there any oil on the antenna>>
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  #7  
Old 09-07-2021, 09:29 AM
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BlackhawkSP BlackhawkSP is offline
 
Join Date: Jun 2011
Location: Indianapolis
Posts: 299
Default Reception Range

Quote:
Originally Posted by Jesse View Post
We are having a problem that I wanted to post here to see if anybody here has a valuable suggestion. In a new RV-10 with a professional audio harness (Approach Fast Stack), we are having problem with receive range on our radios. We have a GMA245 audio panel, a Dynon Com (Trig Transceiver) and a GTN650. This has been an ongoing problem that didn't appear at first, but became noticeable around 10-15 hours from new.

On a test the other day, the plane left here. From our base station radio with an antenna on the top of the hangar, we had great reception for the first couple of miles. The further he got away, the more weak and staticy the plane received, although the transmit was still loud and clear. When the plane was 15 miles away, he could not receive the base station at all, and he was still loud and clear receiving at the base station. In summary, his receive range is very short, but transmit seems to be good, or at least better. This problem is with both radios.



We have verified that we have good coax from both radios. to their respective antennas, which are the RAMI AV-17's, and the coax run down opposite sides of the plane to their respective antennas. Both antennas were new when installed and bought together. We removed some paint where the screws attach the antenna to the airplane, and used lock washers under the nuts after removing primer from where the nuts tighten down, so we know we have a good ground (the antennas are under the pilot and copilot seats). We have tested with each radio powered down and the problem is still with the powered radio, so it isn't cross-talk. We have verified, and added, a good ground from the audio panel to the airframe. We have tried with both pilot and copilot headset alone, with an without the rear headsets, and have tried other known good headsets. We have replaced the Dynon transceiver 2 or 3 times, thinking it was specific to that radio, with no change. The intercom works just fine all the way around. We have swapped with another GMA245 audio panel and there was no change, so it's not a bad audio panel.

The only thing we can think of that is left to check is to replace one or both of the COM antennas. I have never had a bad RAMI bent whip antenna, certainly not out of the box, and the likelihood of two at the same time on the same plane seems even more unlikely, unless they were both from the same batch that happened to be a bad batch, but I don't know how we would change that.

As a side note, this plane has the full EFII system with the buss manager. We are going to test reception range on the ground with the engine on and off soon to see if the engine could be causing any disruption.

Any thoughts?

Can't remember on the GTN 650, but when I recently upgraded to the 650 Xi, I started to have a receive problem with the Xi. In the configuration settings, go to the COM page and make sure the Squelch setting is lowered to 10 percent or less. I was having problems with hearing range till I lowered the default setting. What's weird about yours is that it's on 2 radios (I'm ignorant about the Dynon setup).
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  #8  
Old 09-07-2021, 09:48 AM
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Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
Posts: 11,172
Default I'm missing something........

Quote:
Originally Posted by Jesse View Post
We did the specific testing with the base station because he was seeing the problem in flight. It is not a base station problem.
Not quite sure I understand this logic. If the base station has a weak transmitter or high VSWR on the antenna it would create this scenario.

Does the aircraft receive weak signals from other aircraft and/or other ground stations?

Do other aircraft receive strong signal from your base station?
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Last edited by Mel : 09-07-2021 at 12:05 PM.
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  #9  
Old 09-07-2021, 11:19 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by Mel View Post
Not quite sure I understand this logic. If the base station has a weak transmitter or high VSWR it would create this scenario.

Does the aircraft receive weak signals from other aircraft and/or other ground stations?

Do other aircraft receive strong signal from your base station?
+1

I would go 30 miles from the base station with a different plane and see if it receives from the base station.

Larry
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  #10  
Old 09-07-2021, 11:31 AM
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rocketbob rocketbob is offline
 
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Location: 8I3
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I good tool I use for checking antennas is a NanoVNA which one can get on Amazon for $60.

Here I am sweeping the entire band checking one of Don Pansier's excellent antennas. The cursor is showing SWR at 1.52 at around 122.900mhz.

There could be some bad crimps of the BNC connectors so I would also check at the radio end.
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